| |
Sea
pens
Order Pennatulacea |
|
|
Pteroeides sp.
|
Sea pens belong to the same group as sea anemones and soft corals.
However, while sea anemones are large solitary polyps, sea pens are
actually a group of polyps connected to one another in a colony.
Colony Life: While the polyps
on soft and hard corals are more or less alike, in a sea pen, there
are different types of polyps connected to each other, each playing
a different role. The central stalk is an individual animal, called
the primary polyp, that supports the whole colony. The bottom half
of the primary polyp forms a 'foot' or peduncle that anchors the colony
and retracts the whole colony into the ground at low tide. Other individual
animals emerge from upper half of the primary polyp forming the 'feathers'
on the central stalk. Called secondary polyps or autozooids, they
have stinging tentacles that filter feed at high tide. There are also
another kind of highly modified polyp, called siphonozooids, that
pump water into the colony to keep it rigid, and circulates water
through the colony. The colony might be stiffened by spicules (tiny
bits of calcium). Some have sharp spicules on the edges of the feathery
secondary polyps. Some have a stiff central rod made of calcium carbonate.
 Digging
in: Sea pens are adapted for life on soft sea bottoms.
Here, they can dig into the ground for support. They retract completely
into the soft ground when alarmed or at low tide.
Pen pals: Sea pens are often homes
to other small creatures. The tiny Sea pen porcelain crab (Porcellanella
picta) is often found in the seapen Pteroeides sp.
 Sea
pencils? Sea pens are so named because they resemble feather
quill pens. Some sea pens have small flower-like secondary polyps
that only emerge at night. During the day, without their secondary
polyps, these sea pens look more like sea pencils!
Please do not step on or uproot sea pens. You will hurt a whole colony
of animals and the small creatures that live on them.
Role in the habitat: Some snails
and nudibranchs prey on sea pens.
|
|
Pteroeides sp.
unidentified sea pen
Tiny Crab
Tiny porcelain crab often found in
the sea pen below
Crab Home
Pteroeides sp.
Sea Pencil?
With their secondary polyps retracted
A closer look at the flowery polyps |
|
quick
facts
15-25cm long, sometimes seen in the seagrass lagoon
Classification:
Class Anthozoa
Phylum Cnidaria |
